Angy Peter of Khayelitsha township was to be a key witness before a commission looking into police abuse. Colleagues call her arrest suspicious.

JOHANNESBURG, South Africa — Activist Angy Peter, who has spent years exposing police failures in the sprawling township of Khayelitsha outside Cape Town, was due to testify at an upcoming commission of inquiry.

Instead, she is behind bars, charged with killing a petty thief and police informer, Rowan du Preez, who supporters say Peter once saved from an angry mob that had accused him of theft.

The timing of Peter's arrest and the homicide allegation are both suspicious, say fellow activists from Cape Town's Social Justice Coalition. She was to testify in less than two weeks before a commission looking into the township's policing problems. The commission was established by Helen Zille, premier of Western Cape province.

Colleagues say Peter, 32, is also known for campaigning against mob justice in Khayelitsha, where killings of accused criminals by furious mobs are rife.

Police have declined to make public the details of their case against Peter and fellow coalition member Isaac Mbadu, both charged in the death of du Preez, who was found Oct. 14 severely beaten and burned and later died.

According to her supporters, Peter had been trying to rehabilitate du Preez, at one point urging him to write a letter apologizing to the community for his crimes.

The case is the latest to rile activists in a nation where public confidence in police has never been great in communities like Khayelitsha, where activists accuse authorities of brutality, fatal shootings and a failure to investigate crimes.

The Social Justice Coalition says community members often take the law into their own hands and kill accused thieves, rapists and others because they have no faith in the police or courts. At least 18 people have been killed by vigilante mobs in the township this year, some of them "necklaced" — killed by having gasoline-filled tires placed around their necks and set afire.

The Western Cape inquiry comes three months after police opened fire on protesting platinum miners at the Lonmin company's Marikana mine, killing 34 and wounding 78. Police later arrested more than 270 miners, charging them with the murder of their comrades, relying on an arcane apartheid-era statute, a move that shocked the nation. The charges were withdrawn after a public outcry.

Critics claim that when police officers shot the miners, they weren't firing in self-defense but rather killing in cold blood miners who were falling or hiding in rock crevices. At best, others say, the deaths expose dismal police training. Police officials insist that the officers had no choice but to fire in self-defense.

President Jacob Zuma has ordered a judicial inquiry on the killings, due to be completed next year.

South African Police Minister Nathi Mthethwa has announced that police officials will launch a High Court challenge to the commission set up by Zille after failing to persuade her to call it off.

"Despite the engagements we held with the premier over the past weeks, it is evident she is determined to continue with the commission by hook or crook, which leaves us with no option but to challenge the matter, through the legal framework," he said, according to local news reports.

Like many senior police officials, Mthethwa has been accused in South African news reports of wrongdoing. In April, he denied reports that he had looted a crime intelligence fund to renovate his house.

Gavin Silber, a spokesman for the Social Justice Coalition, said in a phone interview that Peter was seen as a key witness at the Khayelitsha inquiry.

"Without speculating [on the merits of the murder case], the timing is very suspicious because Angy was supposed to testify at the beginning of the commission, which starts on Nov. 12," Silber said. "We have collected more than 60 affidavits from people in Khayelitsha testifying as to how the police have failed them, and she was the one responsible for collecting them. Her efforts to expose police corruption in her areas mean that there are a lot of senior police who will benefit from having her out of the way."

Peter and Mbadu, in prison, were not available to comment, but Silber said they deny the charges. He said Peter recently claimed to have evidence on the corruption of a senior police official, which she planned to present to the commission.

Another prominent Cape Town activist, Zackie Achmat of the Treatment Action Campaign, told the local Mail and Guardian newspaper that the charges against Peter seemed odd.

"Why would she have become involved in the killing of a man she had allegedly been trying to rehabilitate from a life of crime?" the newspaper quoted him as saying.

In the mining inquiry, an advocate for the slain miners' families, Dali Mpofu, on Wednesday accused police of torturing miners who were arrested after the shootings. One was beaten so severely that he lost his hearing, the advocate alleged.

Meanwhile, the South African Human Rights Commission issued a report Wednesday on the police killing of schoolteacher Andries Tatane, 33, in Ficksburg, northwest of Durban, in April 2011. Video aired on television showed Tatane being shot in the chest during a demonstration over poor government services.

The commission said police used disproportionate force and were ill-equipped to deal with the protest. Seven officers face murder charges in Tatane's death.